Autopilot means automatic pilot to every layperson on the street. It doesn't mean maintain heading at this altitude under these specific circumstances. It means the plane flies itself.
It's like trying to argue that a smartphone is a computer. Technically it is but nobody other than those from a technology background would agree.
This is only because Tesla changed the meaning with its "fully self-driving but the government won't let us" marketing lies.
In the common parlance, saying "someone is running on autopilot" means they are going through the usual motions but not really paying attention to what happening or responsive to surprises. Pretty close to the aviation meaning and what Tesla car does.
I believe the point is nobody expects planes, where a layperson would know the term autopilot from, to be left unattended by the pilots. So why should this be assumed on the road?
Because human nature. No matter what they call it, the better it works the more the human driver will relax and let the machine take over. No matter how many times you warn them that that's inappropriate or unsafe.
It's like trying to argue that a smartphone is a computer. Technically it is but nobody other than those from a technology background would agree.